Very strange! I have no idea what could be causing this. 
Maybe something has changed in the upgrade. Was it working before the upgrade?
I noticed this at the end of July after an update, I don’t remember it happening before.
I wanted to check it by reinstalling Volumio in version 3.703, but during system installation the update to 3.742 is forced during the first steps of the initial configuration.
I don’t currently have an older version of Volumio running.
If you use the previous version of the MPD-OLED plugin, it works without any problems.
Can you try one of the previous versions of the mpd_oled plugin?
The only thing changed was some ALSA configuration changes as suggested by @balbuze I don’t know why this would cause issues 24bit playback 
It seems canva works only with 16b datas.
Try this:
modify /data/plugins/system_hardware/mpd_oled/asound/volumioalsa.postalsa.5.conf
and replace the content by (copy paste)
pcm.volumioalsa {
type plug
slave.pcm {
type multi
slaves {
a { channels 2 pcm "postalsa" }
b { channels 2 pcm "mpdoledfifoi" }
}
bindings {
0 { slave a channel 0 }
1 { slave a channel 1 }
2 { slave b channel 0 }
3 { slave b channel 1 }
}
}
ttable [
[ 1 0 1 0 ] # left -> a.left, b.left
[ 0 1 0 1 ] # right -> a.right, b.right
]
}
pcm.mpdoledfifoi { #convert in 16b)
type plug
slave {
format "S16_LE"
rate 44100
channels 2
pcm "mpdoledfifo"
}
}
pcm.mpdoledfifo {
type volumiofifo
fifo "/tmp/mpdoledfifo"
}
disable enable the plugin.
let me know 
Edit : works with softvol! (not sure…)
2 Likes
I installedand and tried version 1.1.2 again,
and it works fine here.
if you want to test this
modify /data/plugins/system_hardware/mpd_oled/asound/volumioalsa.postalsa.5.conf with
pcm.volumioalsa {
type plug
slave.pcm {
type multi
slaves {
a { channels 2 pcm "postalsa" }
b { channels 2 pcm "mpdoledfifo" }
}
bindings {
0 { slave a channel 0 }
1 { slave a channel 1 }
2 { slave b channel 0 }
3 { slave b channel 1 }
}
}
ttable [
[ 1 0 1 0 ] # left -> a.left, b.left
[ 0 1 0 1 ] # right -> a.right, b.right
]
}
pcm.mpdoledfifo {
type volumiofifo
fifo "/tmp/mpdoledfifo"
format_3 "S16_LE"
}
Hello!
After updating the mpd-oled plugin to version 1.1.3, I also had the strange display of the spectrogram bars for audio data in 24 bit and 96 kHz described by “rak39”.
My Ian Canada streamer based on a Raspberry Pi 4 is equipped with a MonitorPi Pro (integrated control center and signal analyzer). It has a built-in signal analyzer (hardware, not Raspberry software) and recognizes the digital audio format and the I2S/DSD signal status in real time and shows the real music information on its OLED display. In the photos it is the display on the right with the rotary control.
Next to it I have installed a 1.3 inch SPI OLED display with the MPD OLED plugin. In the photos it is the display on the left with the blue housing.
I have now tested the 2 solutions suggested by “balbuze” for plugin version 1.1.3 and a downgrade to plugin version 1.1.2.
1. Initial situation with plugin version 1.1.3
The displays of MonitorPi Pro and SPI-OLED see photo. The streamer/DAC is still a test setup, the front panel and rear panel are still missing. Technically everything is fully functional though.
The display of the bars of the spectrogram is strange as described by “rak39”. There are no significant swings in the bass and mids, only something is happening in the treble. In general the bars hardly move.
MonitorPi Pro shows a correct audio output in 24 bits in the 32-bit container in 96 kHz and a clock rate of around 1000 (bottom left in the display). The bit rate shown in the SPI display is typical for an audio file in 24 bits and 96 kHz. The audio output is unchanged in high-res format.
2. Plugin version 1.1.3 with solution 1 from “balbuze” (post 906)
Everything works perfectly. Many thanks to “balbuze”! 
Picture 2 see following post.
The bars of the spectrogram are displayed correctly even for audio files in 24 bit and 96 kHz and move as usual.
MonitorPi Pro shows a correct audio output in 24 bit in the 32-bit container in 96 kHz and a clock rate of 925 (bottom left in the display). The bit rate shown in the SPI display (3111) is typical for an audio file in 24 bit and 96 kHz. Excellent, the audio output is unchanged in high-res format. That’s how it should be.
3. Plugin version 1.1.3 with solution 2 from “balbuze” (post 908)
Picture 3 see following post.
The bars of the spectrogram are also displayed correctly for audio files in 24 bit and 96 kHz and move as usual.
The SPI display shows a bit rate of 2815, which is typical for an audio file with 24 bit and 96 kHz. MonitorPi Pro also shows a sampling frequency of 96 kHz, but a bit rate of only 16 bits. The clock frequency of 641 kHz (bottom left in the MonitorPi display) is significantly lower than with a bit rate of 24 bits (in the 32 bit container). Unfortunately, the audio output is downsampled from 24 bits to 16 bits.
4. Downgrade to plugin version 1.1.2
Picture 4 see following post.
The bars of the spectrogram are displayed correctly. The SPI display shows a bit rate of 3022, which is typical for a 24-bit, 96 kHz audio file. MonitorPi Pro shows a sampling frequency of 96 kHz, but a bit rate of only 16 bits. The clock frequency of 683 kHz (bottom left in the MonitorPi display) is significantly lower than with a 24-bit bit rate (in the 32-bit container). Unfortunately, the audio output is downsampled from 24 bits to 16 bits.
I wrote this text in German and automatically translated it into English using Google. I hope that you can still understand my tests and their results.
hello!
Thanks for a such detailed tests!
Very interesting!
So sol 2 works for you, fine.
Problem, it doesn’t work in some case with software volume and or FusionDsp.
I have to rework…
home made DAC?
Hi guys, Ok I have the same issue on my WEB Radio streamer with the Display and the strange bar graphs in spectrum analyzer. Will wait until Balbuze is ready with coding. If You need support in testing please let me know
